The present invention relates to a lead frame and more particularly to a lead frame loaded with photocoupling elements, a semiconductor device produced by using the lead frame, and a method of producing the semiconductor device.
A double sealed photocoupler belongs to a family of semiconductor devices. The double sealed photocoupler is produced by a procedure including primary sealing using light-transmitting resin and secondary sealing using light-intercepting resin. Japanese Patent Laid-Open Publication No. 9-83013, for example, discloses a double sealed photocoupler in which a lead frame for forming lead forming portions is accommodated in a secondary molding to thereby reduce the size of the photocoupler.
However, lead forming effected on a lead frame for bending the lead forming portions brings about the following problems. Portions where tie bars and opposite outside frames are connected irregularly deform. As a result, positioning holes formed in the outside frames are displaced and prevent the lead frame from being accurately positioned at a stage following the lead forming stage. Moreover, stress ascribable to lead forming remains in the individual photocoupler or product and brings about package crack or similar trouble later.